The Grenjeng River in Indonesia is polluted by industrial, livestock, and domestic waste. Water quality was assessed using physical-chemical and biological parameters. Results showed high levels of BOD, COD, and total coliforms, exceeding water quality standards. The Pollution Index indicated the river water was polluted to extremely polluted in the dry season and moderately polluted to polluted in the rainy season. Dumping waste into rivers directly impacts water quality, affecting irrigation water for agriculture. To prevent further pollution, an environmentally friendly approach is needed, including increasing public awareness and implementing integrated wastewater treatment systems.